A compressor configured to compress a gas and supply the compressed gas to a machine or the like connected to a downstream side thereof is known. As such a compressor, there is a compressor that can control a flow rate. For example, a compressor system includes an inlet guide vane of the compressor installed at an upstream side of an impeller, and introduces a gas to the impeller via the inlet guide vane. Then, the compressor system controls the flow rate of the gas introduced into the impeller by regulating an opening of the inlet guide vane.
In addition, the compressor system may include a multi-stage impeller from an upstream side toward a downstream side of a gas flow (for example, see Patent Literature 1). Further, in order to increase a flow rate, there is a compressor system including a plurality of impellers installed at the most upstream side, and configured to join the gas compressed by the plurality of impellers and then introduce the gas into the impeller of the downstream side. In such a compressor system, there is a method of controlling an introduction flow rate to the plurality of impellers connected to the most upstream side in parallel at the same period of the opening degrees of the inlet guide vanes disposed at the upstream side of the impeller (i.e., the opening degrees become equal to each other) and controlling a state of the ejected gas. For example, the compressor system includes the inlet guide vanes installed at the inlet ports of the plurality of impellers at the most upstream side. Then, the compressor system controls the opening degrees of the inlet guide vane to be equal to each other, and controls a state of the ejected gas.